CULTIVATION OF ANAEROBIC BACTERIA. 183 



third of their length, are 

 used. These are filled 

 with about 10 c.c. of 

 nutrient medium, then 

 closed by a cotton plug, 

 and after inoculation 

 are immersed in water 

 at about 3o-35 C., and 

 then connected with an 

 air-pump. The air is all 

 driven out by the water 

 vapour given off under 

 the diminished pressure, 

 whereupon the narrow 

 part of the tube is closed 

 by fusion and the upper 

 portion removed. By the 

 use of nutrient gelatin this 

 method also facilitates the 

 cultivation of colonies, 

 so that the individual 

 anaerobic species in a 

 bacterial mixture can be 

 isolated. For this pur- 

 pose the still warm liquid 

 contents of the tubes are 

 converted into Esmarch 

 roll-cultures, as shown in 

 Fig. 46- 



In place of removing 

 the air from the culture 

 vessel by mechanical 

 means pumping or driv- 

 ing it out by vapour 

 recourse may be had to 

 oxygen-absorbing chemi- 

 cals. For this purpose 

 a solution of pyrogallic 

 acid [v-C 6 H 3 (OH) ? ] in 

 caustic potash, a mixture 

 that takes up oxygen 

 with avidity, and which, 

 as is well known, has 

 long been in use in gas 

 analysis, is employed. It 

 was introduced into phy- 

 siological work by Nencki 

 in 1880, as a test for 

 the presence of anaerobic 

 organisms, but it was not 



FIG. 46. 



Gruber's anaerobic tube 

 exhausted of air.| jj j 



Upper portion removed by 

 fusing. Contents ar- 

 ranged as an Esmarch 

 culture wherein the 

 germs have developed 

 to colonies. Some- 

 [what reduced in size. 

 (After Gruber.) 



FIG. 47- 

 Buchner's anaerobic tube. 



The pyrogallol solution is 

 at p, the wire support 

 resting therein and 

 carrying the test-tube 

 with the inoculated nutrient medium (n). Some- 

 what reduced. (After Buchner.) 



